Hi, been a while. I’ve had my tc88A recently rebuilt at 180000 km. It now has a S&S 4 3/8 crank wiseco 9.6 forged flattops,my barrels bored to 95”,my stock heads cleaned up with new exhaust valves and beehive valve springs. I’m assuming it has a stock head gasket. I’m running se 211 cams,a 42 mikuni hsr and a Vance and Hines pro pipe h/s. It’s putting out some pretty decent torque and power at 96hp and 105lbft of torque,on the builders dyno anyway. This builder dyno’ed using the stock 160 main jet stock 97 needle 20 pilot 70 accelerator pump nozzle with the needle clip position 1 notch leaner to improve the cruise economy. I have since tried some different main jet sizes and at the moment it has a 167.5 in it. I also have a twin tech ignition which I’m never quite sure if I’ve got it set right. The reason for all my concern with the tuning is the motor has a tendency for spark knock,especially top gear roll ons up gradients and even around the 120 140 kph mark. It has been suggested that I only run 98 fuel where as I only ran 95 in the past. I took it for a run yesterday up the same hill around the same speed and with the ignition set at 1 initial and 2 advanced still pinged when cracking the throttle, although only lightly. I have no idea what actual compression this motor would be putting out ,and any thoughts would be appreciated. Also the builder had the ignition set on 2 initial and 5 advance. So is it my ignition settings or carb settings or both? Maybe I’ll just have to live with it😂

Plug all your details into this:

Thanks for replying John. I’ll take your advice and and throw my info at the mob you suggested and see what they say. I’ve pissed the guy off that built the engine and he’s not very forthcoming with what he did on the build,but no matter. I’ll do a comp test and let you know the figures.98 fuel has decreased most of the knocking but I moved the initial timing back to 2 and the advance back to 1 and this seems to have eliminated 98% of the pinging.

It's just an online calculator, not a service or person etc. It makes it hard without the info. 

No worries👍🏼

Compression would be closer to 9.2:1 with stock chamber heads, and 8.3 corrected.

I'm also a bit confused, you have a 4 3/8" crank, but you mentioned bored to 95" ?

Yes speedster I mean it’s a 103 cube now with the stroker crank and my 88 barrels bored to suit. I ran it over another blokes dyno twice after the original run on the builders dyno, once with the 160 main jet and again with a 165 main and his figures were 96 hp 105 ftlb and 97 hp 104 ftlb respectively. Two totally seperate runs on different machines both on smoothing 5. The bike has good low end and midrange.I’ve read plenty about this cam supposedly matched to higher compression but it seems to work fine in this combo.If my comp is as low as we think then why the need to retard my ignition as much as I have ie. initial 2 advanced 1 to counter pinking in top gear roll ons? I pestered this builder with all these questions, he wasn’t forthcoming with answers so it’s still a mystery to me.

Thanks mate I’ll do that soon and I’ll let you know how it goes👍🏻

Gday Hoody’ regarding the circuit to tune to help eliminate roll on pinking, my needle is the stock 97,one clip position leaner than the stick middle position,needle jet stock,accelerator pump the stock 70. Air filter is a round k&n. Breather has been redirected to ground via a hose . I’ve tried different main jets on a straight road flat out to try to determine correct size that way for that part of the circuit and to me the 160 was a bit lean but produced good power so I thought I would bump up that jet size to be on the safe side. Your opinion is much appreciated. Cheers Gazz.

Thanks Hoody are you saying I should run stock jetting and settings on my Mikuni even with a bigger motor than what I had. I had all stock settings on the old motor which was a stock 88 with 203 cams. I have 211 cams now and a 103. Stock 88 head. My dtt settings at present are initial 2 advance 1 with multi spark enabled. Pinging is now only light rolling on up a gradient but it’s still there. Also on these ignition settings I’ve noticed it doesn’t kick back which it did on hot start up’s sometimes. There is some bigger chunks of metal in my primary these days which I’m assuming is bits of starter pinion and clutch ring.

Hi Gazman the guys are right there ,have a compression check.

Yep will do and thanks for your input Uncle. Just waiting for my dodgy back to come right now🙄

Cheers thanks Hoody really appreciate your input,as soon as my cactus bulging discs settle I’ll get the comp test done hot and take it from there.👍🏼🙂

Don’t know if these pics of my dyno reports will be clear.

The report without the a/f is the one from the builder dyno and the other from a mates dyno showing a/f . The blue line on the mates was with a 160 main,and the red with a 162.5 main.

Thanks Speedzter and yes it all works surprisingly well with these cams. I know for sure that he used my original heads with beehive valve springs,new exhaust valves but I don’t know what head gasket he used.The mate that did the last dyno runs took it for a spin and he was impressed with the low to midrange. Also he moved the needle clip back to the original mid position and it still pinged its tits off through the gears wot.I have that clip position set one position leaner now which is where the builder had it to improve my cruise economy. I’ll get a hot comp test done soon and see what I’ve got. Im in Tassie,do know of any competent tuners down this way?

Hi Hoody just getting back to you with my hot comp test figures showing 180 psi on the front and 175 on the rear. Test was done at outside temp 20c with a repco tester. I have played with the dials on my dtt ignition and have found initial 0 slope 2 with multi spark turned off by far the best settings I’ve tried so far regarding overall performance and detonation. I’ve done 16500km on this 103 now and does use some oil between changes but I’ve discovered the wiseco forged pistons and rings I ordered have maybe 2 thou piston to skirt clearance and this may account for this. If I’d listened to the builder and went with cast 103 pistons I may not have had this problem. Cylinder to skirt I mean.

Gday speedster getting back with my comp testing , 180 psi front cylinder and 175 rear psi. A little difference, done 16500 km on this motor now and it uses some oil between changes bearing in mind that I opted for wiseco forged flattops and I’ve only recently discovered these run about 2 thou clearance cylinder to skirt. May account for that. Spark knock has settled heaps on the dtt at initial 0 slope 2 , pulls well.